In continuous ink jet printing, ink is supplied under pressure to a manifold that distributes the ink to a plurality of orifices, typically arranged in linear array(s). The ink is expelled from the orifices in jets which break up due to surface tension in the ink into droplet streams. Ink jet printing is accomplished with these droplet streams by selectively charging and deflecting some droplets from their normal trajectories. The deflected or undeflected droplets are caught and re-circulated and the others are allowed to impinge on a printing surface.
The printhead for a continuous ink jet printing apparatus is usually required to be replaced after a certain number of hours of use, typically as a result of failure, then returned to the manufacturer for refurbishing. Unfortunately, removing the printheads and, consequently, reinstalling printheads, is time consuming and subject to error.
For example, when the printhead on a one-inch printer is removed, it is necessary to first remove printer system covers, revealing all components of the controller and printhead, then disconnecting multiple electrical connections, fluid connections, and back-off fasteners retaining the printhead.
Similarly, on a four-inch printer, the printhead and controller are built as one unit and must be removed as a unit, necessarily involving disconnecting all electrical and fluid lines at the unit, then disconnecting two latches. The unit is then lifted away from its mount.
U.S. Pat. No. 4,809,015 discloses one method for accomplishing printhead installation and retainment. In the '015 patent, the means to support the printhead were located under the printhead. While that was acceptable for a drum printer, it is not appropriate for a printer which prints on a flat base where the support means would require a large print distance. The '015 patent utilized a over center cam latching action to secure the printhead. While the over center cam latch mechanism works appropriately for small printheads, when scaled to a much larger, heavier long array printhead such over center cam latches require much stronger bias springs. While the printhead is being secured by such a mechanism, as the latch passes the overcenter point, the needed strong springs tend to engage the printhead in the nesting hardware too abruptly. This can result in damage to the mating fluid and electrical connections. It can also pose a pinching or smashing hazard to the fingers of the operator. For these reasons the method of the '015 patent cannot be readily adapted for use with long array ink jet printer systems.
A need has therefore been identified for an easily replaceable printhead for use with various size printers.